The Italian Supreme Court handling Amanda Knox's murder case released its reasoning today and cited prosecutors' early theory that her roommate Meredith Kercher died in an "erotic game" that got out of hand, a motive that the prosecution abandoned during the initial trial.

Knox spent four years in prison after being convicted of Kercher's 2007 murder in Perugia, Italy, where they were roommates while studying abroad. Kercher was from England while Knox was from Seattle.

An Italian appeals court threw out her murder conviction in 2011. In March, however, the Italian Supreme Court rejected the Appeals Court ruling and ordered a new trial for Knox and her ex-boyfriend Raffaele Sollecito.

The Supreme Court today filed its "motivation," a written document that spells out the court's reasoning.

The court's 74 page document indicates that the Supreme Court judges supported the prosecutors' original theory that Kercher possibly died during a forced "erotic game" that got violent, according to the Italian news agency AGI.

The Supreme Court judges are not judging the merit or worth of the testimony or evidence, but rather the process that the Appeals Court used to reach its verdict.

The judges said the appeal had to be annulled "due to the multiple shortcomings, contradictory events and manifest lack of logical reasoning."

The sex game gone wrong theory was initially suggested by the prosecutors, but the motive later evolved during the trial into simmering enmity between the women because Knox allegedly brought boys home late at night and was sloppy, and Kercher allegedly accused her of stealing money. The prosecution ended the first trial by telling the jury sometimes people commit violence without a motive.

The judges' document mentioned looking at a "wide range of possible hypothetical options," including "the change in a program which at first only included the involvement of the English young woman in a sex game which she didn't share, to exclusively forcing her into a group kinky erotic game, which exploded, getting out of control."

Knox's lawyer Carlo Dalla Vedova said he disagreed with the court's ruling.

"We respect the Supreme Court's decision, but we do not agree with it," Vedova told ABC News. "All the facts the discuss were analyzed already. So now we simply re-start and re-do the case. We are ready to start again in Florence, and we are looking forward to defending Amanda. She is completely innocent."

Vedova said that since the same evidence will be presented as in the appeals court that acquitted Knox, "We expect the same results. We are not worried."

The defense attorney for Sollecito said the ruling was not a surprise to her.

"It is more or less what we expected," attorney Giulia Bongiorno told Italian news agency ANSA. "The Supreme Court has in fact asked for a deep analysis of the investigation and evidence. But we don't fear any further analysis."

"If there was an erotic game they should find the other protagonists as they are certainly not Raffaele Sollecito and Amanda Knox," Bongiorno said.

"The scientific evidence proves in fact that there are no DNA traces of Sollecito and Knox at the scene of the crime," she said.

The judges also pointed out a number of other issues in the "motivation" that they reportedly believe were not properly dealt with including specific witnesses and timeline issues.

Amanda Knox Court Suggests Sex Game Caused Murder

The judges believe that the testimony of a shop owner who allegedly saw Knox buying detergents hours after Kercher's death must be taken into consideration and not dismissed as the appellate court judges did, according to ANSA. The shop keeper did not come forward with his information until weeks after the murder.

They also suggested the Appeals Court was wrong to dismiss the testimony of a key witness as unreliable simply because he was a homeless person who frequented a public square. The man claimed he saw Knox and Sollecito with Guede near the park the night of the murder, which took place the day after Halloween.

In the appeals trial, he said he was sure he saw the three of them together because he remembered the presence of the buses which took students to clubs on Halloween.

The judges also wanted to clarify how many people were at the scene of the crime the night Kercher died and the precise time of her death, according to ANSA.

Knox's lawyer, Carlo Dalla Vedova, told ABC News in April that he expects a new trial to begin in the next year. The trial is at the appellate level again and will take place in Florence, Italy.

In April, Knox told ABC News' Diane Sawyer that the Supreme Court's decision to order a third trial was "incredibly painful."

"I felt like after crawling through a field of barbed wire and finally reaching what I thought was the end, it just turned out that it was the horizon," Knox said. "And I had another field of barbed wire that I had ahead of me to crawl through."

Knox does not have to return to Italy for the trial, and extradition is not currently on the table.

If she is convicted again, that ruling would most likely be appealed up to the Italian Supreme Court.

Only if the Supreme Court upholds the guilty verdict could extradition even begin.